Field of the Invention
This device is directed to devices for rotatably adjusting such structures as antennas used in satellite communications.
It is known that antennas for communication with satellites must be able to scan a demi-sphere centered on the vertical axis of a fixed pedestal. To that end, it is necessary to combine movement along two planes, the first in azimuth, or in a horizontal plane, the second in elevation, i.e. in a vertical plane.
For average structures, namely those with a diameter less than or equal to 13 meters, the movement in elevation is obtained by a jack which allows the antenna to pivot through about 90.degree., while the movement in azimuth is obtained by two gear motors on the shafts of which are fixed pinions which mesh with a fixed ring gear whose diameter is about 1.5 meter. The gear motors, which are normally adjustable, are disposed symetrically and are secured to the assembly rotating with the antenna. The gear motors allow rapid movements (homing mode to change aiming) and slow movements (tracking mode).
When antennas are employed whose diameter is greater than or equal to 16 meters, the movement in elevation is still obtained by a jack as for the average structures, but the movement in azumith, made by two gear motors, requires a ring gear of large diameter (about 4 meters) in order to maintain structural rigidity taking into account the increase in mass. This is both expensive and cumbersome, with the result that the solution adopted consists in a configuration with mean clearance allowing displacements by bounds of 60.degree. with an overlap of 30.degree..
This configuration with mean clearance is hardly more satisfactory than that using a large-diameter ring gear.